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If an arithmetic sequence has a1=5 d=-2 and n=18 what is sn?

User Galadog
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1 Answer

3 votes

Answer:

sn = -216

Explanation:

If an arithmetic sequence has a1=5 d=-2 and n=18 what is sn?

The formula for sn is given as:

sn = n/2[2a +(n - 1)d]

Hence, we fill in our values

sn = 18/2 [2 × 5 + (18 - 1)-2]

sn = 9 [ 10 + (17)-2]

sn = 9 [10 - 34]

sn = 9 × -24

sn = -216

User Jrovegno
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